Alkylthiopurines and method



United States Patent 3,135,753 ALKYLTHTOPURINES AND METHOD George H. Hitchings, Tuckahoe, and Gertrude B. Ehon, Bronxviile, N.Y., assignors to Burroughs Wellcome & Co. (U.S.A.) Inca, Tuckahoe, N.Y., a corporation of New York No Drawing. Filed May 10, 1961, Ser. No. 108,986 4 Claims. (Cl. 260-252) This application relates to a new group of alkylthiopurines which have valuable properties in medicine as described below. These new compounds can be represented by the following Formula 1:

wherein R is a lower alkyl group and Z is a bivalent radical selected from the class consisting of alkyl-N alkyl-N O I S and i H C These new compositions of matter may be prepared from the corresponding oxygen compounds of Formula 2 by treatment with phosphorus pentasulfide in an inert solvent at an elevated temperature but at a temperature substantially below the decomposition point of the starting material and product.

This application is a continuation-in-part of application 663,912 filed June 6, 1957, now abandoned.

These new compositions are valuable medicaments and in particular are useful because of their ability to increase the blood flow in the coronary vessels, to improve the circulation in the heart muscle and to relieve the symptoms of angina pectori. In this regard, they are notably superior to other methylated purines which heretofore had been used in medicine for this purpose. This can be illustrated and measured by their effects on isolated heart preparation known as the Langendorfi preparation. This is illustrated in the table below wherein three of the compounds of this application have been subjected to measurements on the Langendorfi heart preparation in comparison with aminophylline. The coronary flow index is the product of both flow and potency, i.e. if a drug doubled the fiow over what was given by aminophylline and at one half the dose of the latter, the value of the index would be 4. The following examples serve to illustrate the invention, however, its scope is defined in the claims.

A mixture of 4.3 g. of 3-methylhypoxanthine, 12 g. of

Patented June 2, 1964 EXAMPLE 2 2,6-Dithi0the0phylline A mixture of 10 g. of theophylline (1,3-dimethylxanthine), 50 g. of powdered phosphorus pentasulfide and 150 ml. of tetralin was heated for 5 hours at 190 with mechanical stirring. The mixture was cooled, filtered and the insoluble residue washed with benzene and petro leum ether. The residue was boiled with 750 ml. of water for 20 minutes and then chilled and filtered. The insoluble material was treated with 300 m1. of 0.2 N sodium hydroxide, filtered and the filtrate acidified with acetic acid to pH 5. The yellow precipitate of 2,6-dithiotheophylline (5.2 g.), after recrystallization from ethanol melted at 252-254 dec. its ultraviolet absorption spectrum showed maxima at 252, 297 and 345 my. at pH 1 and at 265, 295 and 345 mu at pH 11.

EXAMPLE 3 6-Th'ioiheophylliize A mixture of 5 g. of theophylline, 15 g. of powdered phosphorus pentasnlfide and ml. of dry pyridine was heated under reflux conditions for 2 hours. The pyridine was removed by distillation and the residue boiled with 200 ml. of water and chilled. The insoluble material was collected, treated with 20 ml. of 2 N sodium hydroxide and 200 ml. or" water and filtered. The filtrate was acidified with acetic acid to pH 5 and the crystalline precipitate of 6-thiotheophylline (3.5 g.) collected. After recrystallization from 95% ethanol, the pale yellow crystals melted at 315-317 dec. The ultraviolet absorption spectrum of the product showed maxima at 270 and 342 mu at pH 1 and at 260 and 340 m at pH 11.

EXAMPLE 4 3-14 eflzyl-2-Ox0-6-M ercaptopurine EXAMPLE 5 3-Methyl-2,6-Dithi0xanthine A mixture of 5.6 g. of 3-methyl-2-thioxanthine, 20 g. of powdered phosphorus pentasulfide and 250 ml. of dry pyridine was heated under reflux conditions. The mixture was evaporated to dryness under reduced pressure and the residue heated with 300 ml. of water for 20 minutes and chilled. The crude precipitate was dissolved in 300 ml. or" water containing 20 ml. of concentrated ammonium hydroxide and filtered. Upon acidification to pH 4 with concentrated hydrochloric acid, the 3-methyl-' 2,6-dithioxanthine precipitated (3.2 g.). It did not melt below 340". The ultraviolet absorption spectrum showed 3,135,753 j r 3 r 4 maxima at 254, 298 and 352 111p. at pH 1 and at 257, 302 and and 342 my atpH 11. i What we claim is: i N 1. Compounds of the formula f n s 5 N V 2. 3-methy1-6-purinethione. m 3. 2,6-dithiotheophyl1ine.

Z W r 4. 3-methy1-2,6-dithioxanthine. 7 A 10 References Cited the file of this Patent 7 I H V UNITED STATES PATENTS wherein R is 'a lower alkyl group and Z .is a bivalent Y 7 9 I Hitchmgs et T 1954 radical selected from the class consisting of I V 7 FOREIGN PATENTS v 15 100,875 Germany Nov. 30, 1898 lower alkyl-N 7 lower aJkyl-N V I v I SIC! V H OTHER REFERENCES 0:0 7 Fieser et 211.: Organic Chemistry, pp. 220-227; 2nd ed.

Patent No. 3 l35 753 June 2 1964 George H. Hitchings et ale It is hereby certified that er ent requiring correction corrected belo ror appears in t he above numbered petand that the said Letters Patent should read as Column 3 claim l lines 15 to 1 below instead 0 8 should appear as shown 1? as in the patent:

lower alkyl-ITI lower alkyl-IFI 0:0 V 5:0

Signed and sealed this 29th day of September 1964,

:SEAL) fittest:

ERNEST W. SWIDER EDWARD J. BRENNER Lttesting Officer Commissioner of Patents 

1. COMPOUND OF THE FORMULA 